linux-kernel - Re: [PATCH 3/6] media: qcom: camss: csiphy-3ph: Add Gen2 v1.2.2 two-phase MIPI CSI-2 DPHY init

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Date: Mon, 24 Jun 2024 05:37:48 +0800
From: george chan <gchan9527@...il.com>
To: "Bryan O'Donoghue" <bryan.odonoghue@...aro.org>
Cc: Konrad Dybcio <konrad.dybcio@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Todor Tomov <todor.too@...il.com>, Mauro Carvalho Chehab <mchehab@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	cros-qcom-dts-watchers@...omium.org, Bjorn Andersson <andersson@...nel.org>, 
	linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] media: qcom: camss: csiphy-3ph: Add Gen2 v1.2.2
 two-phase MIPI CSI-2 DPHY init

On Sun, Jun 23, 2024 at 7:17 PM Bryan O'Donoghue
<bryan.odonoghue@...aro.org> wrote:
>
> On 22/06/2024 14:43, george chan wrote:
> >     FWIW 1.2.2 seems to be the desired one: [1]
> >
> >     Konrad
> >
> >     [1]
> >     https://git.codelinaro.org/clo/la/kernel/msm-4.14/-/blob/UC.UM.1.0.r1-02500-sa8155.0/arch/arm64/boot/dts/qcom/atoll-camera.dtsi#L22 <https://git.codelinaro.org/clo/la/kernel/msm-4.14/-/blob/UC.UM.1.0.r1-02500-sa8155.0/arch/arm64/boot/dts/qcom/atoll-camera.dtsi#L22>
> >
> >
> > Here is the log from sm7125 joyeuse phone, not sure if it helps or not.
> > [  204.034767] qcom-camss acb3000.camss: CSIPHY 3PH HW Version = 0x01000000
> >
> > I carefully looked into this csiphy_2ph_v1_2_2_reg of various trees, and
> > concluded below version:
> > (1)atoll, sdm845[1]
> > (2)surya[2], sa8155, factory-trogdor-13443.B-chromeos-5.4[3]
> >
> > I was tempted to use (1)atoll one but it looked like (2) is newer. Is it
> > worthy to create CAMSS_7125 specially for SM7125. Please give me some
> > advice about it.
>
> So, which have you tested with as verified and working ?
>

Tests show me, under my sm7125 test phone test case, no matter v1.2.1,
or atoll's v1.2.2 even surya and trogdor tree v1.2.2 are all
surprisingly works. Thanks for telling me or I won't be able to spot
this out. These results are quite funny :-)

> My assumption here is that this series has been tested and is proven to
> work.
>
> Version 1.2.1 and version 1.2.2 don't indicate different versions of the
> init sequence but different versions of the PHY.
>
> For example - the CSI decoder is "just" digital logic, the "source code"
> for the at logic can be "recompiled" for a different process node.
>
> But the PHYs translate analogue signals into the digital domain and
> therefore will vary with different process nodes - 3nm v 4nm v 28nm.
>
> So it is virtually impossible - or highly improbable that init sequence
> 1.2.1 and init sequence 1.2.2 will work on the same piece of hardware.
>

Yes, agreed. I also have the feeling of sc7180(10nm) vs sm7125(8nm) fab.

> So its not a question of choosing the newer version - only one version
> will work - the version that is specifically tuned to the PHY for the
> given process node and RTL version.
>
> Err, so TL;DR you _have_ tested this and gotten data delivered to you in
> user-space - right ?

User-space tool can't tell so I made some guesses.

A side note, atoll's reg sequence is a bit shorter and, unlike
trogdor, it does not write upto 0x9xx reg. That seemed to me, using
atoll's init sequence for sc7180 is nothing wrong initially. Later on
today, I am wondering if writing those extra regs(> 0x9xx) is to
stabilize the phy, so applying trogdor init sequence to atoll might be
more desirable.

As the trogdor tree with kernel 5.4 so this is a side proof that
trogdor init sequence is newer than atoll's. So I will use the
trodgor's init sequence for CAMSS_7180.

So here is the plan. Let's treat CAMSS_7180 to both sm7125 and sc7180
SOCs, and apply the idea to all others sharing v1.2.2 phy atm.

If somebody knowledgeable could confirm some real difference, then I
can prepare another CAMSS_7125 patch-set afterward.

>
> ---
> bod